Field of the Invention
The exemplary embodiment(s) of the present invention relates to a field of a method of surface modification. More specifically, the exemplary embodiment(s) of the present invention relates to a method of modifying surface for substrate including polydimethylsiloxane (PDMS).
Description of Related Art
Microelectromechanical system has been rapid developed for decades. It combines microelectronic technology and mechanical engineering, and provides electrical machineries with operation scale within microns. Currently, the microelectromechanical system has been widely applied to a number of fields by various processing technologies. Among those fields, microfluidics are made by integrating the miniaturized testing instruments and flow channels onto a chip via microelectromechanical system processing technology, greatly decreasing examining cost and increasing analyzing efficiency. With sampling, mixing, reacting and detecting samples (fluids) in the micro-tube, the problem such as consumption of reagents, human pollutions, etc. may be reduced. It is also called a microfluidic system, such as, biomedical chips, gene chips, protein chips, etc., which is widely applied in the field of medical examination, food examination, and environment examination.
At present, the known materials for manufacturing the microfluidic system include organic silicon compounds, in which polydimethylsiloxane (PDMS) is most common one. The chemical structure of PDMS is shown as:
which is a high polymer of an organic silicon compound. The liquid phase of PDMS is sticky, inert, non-toxic and low volatility; the solid phase of PDMS is a type of silicone, with the characteristics of optical transmittance, and in general, inert, non-toxic and non-inflammable. In the application of the biomedical chips, the high optical transmittance and high elasticity may make the biomedical chips fit into requirements of various examining conditions and situations. In addition, for PDMS, the cost is much lower and the manufacturing process is faster, which are beneficial for industrial manufacturing processes.
While the surface of the PDMS in solid phase is highly hydrophobic, it is not suitable for applying the PDMS in solid phase to the biomedical chips and the microfluidic system. When PDMS is utilized for manufacturing the biomedical chips, it is needed to modify the surface of the PDMS and make it from hydrophobic to hydrophilic.
Known surface modification technologies in the art comprise: (1) plasma treatment: (2) pre-mix/pre-doping with chemicals (Materials Science. 2012, 729, 361-366); (3) covalent modification (RSC Adv., 2015, 5, 7423-7425), etc. Those surface modification technologies in prior art convert the hydrophobic alkyl groups on the PDMS surface to the groups with polarity, e.g. hydroxyl groups, to enhance a hydrophilicity of the PDMS surface. However, the hydrophilicity of the PDMS surface after modification by above-mentioned technologies will be rapidly degraded in short periods of time, the transparency of the PDMS solids will be decreased and the ability to attach to other materials will be reduced. Further, the steps of some of modification processes are complicated and time-consuming, and cost great fortune, which are not benefit for industrial massive production.